Browsing by Author "Jayasree Sankar, S"

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Carbon pools in Lateritic soil amended with coirpith-vermicompost and its effect on Tomato (Solanum lycopersicum L.)
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2019) Aiswarya, R; Jayasree Sankar, S
Characterisation of soil and water of Palakkad eastern plains in relation to growth and nitrogenase content of Azolla spp
(Department of soil science and agricultural chemistry, College of Horticulture,Vellanikkara, 2015) Bhavyasree, K T; Jayasree Sankar, S
study intended for “Characterization of soil and water of Palakkad eastern plains in relation to growth and nitrogenase content of Azolla spp.” was undertaken in the Department of Soil Science &Agricultural Chemistry, College of Horticulture, KAU, Vellanikkara during 2013-2015. The objectives of the study were to conduct a survey of Azolla spp. in the rice growing tracts of Palakkad eastern plains and to identify soil and water quality parameters congenial for the growth and nitrogenase content of Azolla spp. The preliminary survey conducted in the four block panchayaths of Palakkad eastern plains to identify the prevalence of Azolla revealed two blocks viz. Chittoor and Kollengode to be positive with respect to Azolla and hence, further study was restricted to the grama panchayaths of these blocks. Characterization of soil and water was done in both Azolla growing and non-growing regions. Composition of Azolla collected from different locations was also determined. In order to ascertain the nitrogenase enzyme activity, samples of Azolla collected from five different locations were subjected to Acetylene Reduction Assay (ARA). Among the soil parameters, significant difference was noticed between Azolla growing and non-growing locations with respect to pH , EC, organic carbon, available N, P , total Fe, Mn and Zn in contrast to potassium and copper which did not show any pronounced variation. Soil pH, EC, available P, total Fe, Mn and Zn were comparatively lower in Azolla growing regions. However, available nitrogen in soil was more in Azolla growing locations. Heavy metals like Cd, Cr, Ni and Pb were below the detectable limits in soil. Analysis on flood water quality showed significant effect in the Azolla growing regions on parameters like pH, temperature and dissolved oxygen, Fe, Mn, Zn and Cu. Soil analysis data revealed the pH, EC, soluble Fe, Mn, Zn and Cu to be lower under Azolla growing conditions. Heavy metals like Cd, Cr, Ni and Pb were below the detectable limits. Presence of Azolla decreased the flood water temperature but increased the dissolved oxygen content. On comparison, the composition of Azolla revealed a prominent and significant correlation with location on its content of carbon, nitrogen, phosphorus, potassium and also the C/N ratio. Moisture content varied from 94 to 95 per cent, variation in carbon and nitrogen content was from 22.9 to 39.5 per cent and 2 to 4 per cent respectively among the locations studied. The C/N ratio ranged from 9 to 14. Crude protein content of Azolla registered values between 16 and 22 per cent. The content of phosphorus ranged between 0.20 and 0.23 per cent whereas that of potassium was in the range of 1.2 to 1.5 per cent. Correlation worked out between soil parameters and composition of Azolla disclosed a significant positive effect of soil P on the nitrogen, crude protein and phosphorus content of Azolla. However, soil P was negatively correlated with the C/N ratio of Azolla. Nitrogenase enzyme activity quantified was profoundly affected by the locations. The amount of ethylene produced extended from 192 to 236 nmole ethylene g-1 h-1. It showed a significant negative correlation with soil pH and EC. The study has given valuable information on the influence of soil and flood water quality parameters and locations on Azolla which could be used for further investigations on its nutrient dynamics.
Effect of continuous application of rice husk ash (RHA) on inceptisols of palakkad eastern plains
(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 2016) Rincy Rose T John; Jayasree Sankar, S
Jaivakeedanasinikal
(Kerala Agricultural University, 2000) Estalitta, S; Seema, B; Jayasree Sankar, S
Nutrient dynamics and crop productivity in lowland lateritic soil (aeu 10) under rice residue management practices
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Amritha, K; Jayasree Sankar, S
The present investigation was undertaken at College of Agriculture Vellanikkara, Kerala Forest Research Institute Peechi, and Agricultural Research Station Mannuthy during 2017-2020. The experiment comprised of characterization of rice residues and their products for physical and chemical properties, an incubation experiment to study the kinetics of carbon mineralization, and a field experiment to evaluate the efficacy of rice residues and their products on lowland rice. Straw and husk, the important residues produced during the cultivation and processing of rice, respectively was procured from farmer’s field and further materials required for the research work viz., vermicomposted rice straw (VRS), vermicomposted rice husk (VRH), rice straw biochar (RSB), and rice husk biochar (RHB) were produced from the straw (RS) and husk (RH) using vermitechnology and pyrolysis. Recovery from vermicomposting was more (74.38 % for VRS and 70.03 % for VRH) than when the residues were converted into biochar through pyrolysis (19.86 % for RSB and 38.00 % for RHB). Vermicomposting and pyrolysis reduced the bulk density of raw materials. Rice residues and their products were alkaline, with biochar exhibiting the highest level of alkalinity (9.24 for RSB and 9.20 for RHB). The electrical conductivity increased both by vermicomposting and pyrolysis. Straw was comparatively superior to the husk in respect of C, N, K, Ca, Mg, Fe, Mn, Cu, and Zn. However, husk was superior in P, S, B, Si, cellulose, and lignin. Vermicomposting helped to concentrate the nutrients viz., N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, and Si while reducing that of carbon, cellulose and lignin thereby narrowing down the C: N ratio. However, C: N ratio increased upon pyrolysis. Surface morphology of rice residues and their products were studied using scanning electron microscope (SEM). The SEM micrographs of straw and husk exhibited a complex morphology with cell wall composition. SEM micrograph of VRS showed highly fragmented, disaggregated and porous structure which could not be visualised in VRH, may be because the technology of composting using earthworms was more suited to decomposing rice straw than its husk. The SEM analysis showed that the structure of biochar was porous, fragmented and particles gave a broken or distorted appearance thus resembling the plant structure. The structural chemistry of rice residues and their products were analysed using fourier transform infra red spectrometer (FT-IR). Each peak is characteristic of correspondingfunctional group and it clearly explained the presence of C, H, O, N, and Si in the residues and products. Silicon, a major component in the chemical structure of rice material was illustrated by Si-O-Si and Si-H bond in FT-IR spectra. Vermicompost had significant level of nitrogen rich compounds and low level of aliphatic or aromatic carbon compounds compared to biochar, as confirmed by the FT-IR analysis. The FT-IR spectra of RSB and RHB revealed its aromatic and recalcitrant nature. The incubation experiment was conducted for 110 days at 15, 25, 35 and 45 oC to study the kinetics of carbon mineralization in lateritic soil over time, wherein the CO 2 evolution was determined at frequent intervals and the data were used for determination of carbon mineralization and mineralization kinetics. Lateritic soils (100g) collected from Agricultural Research Station Mannuthy, were treated with rice residues and their products (5t ha -1 ), FYM (5 t ha -1 ), and soil test based nutrient recommendation. An absolute control without the addition of organic/inorganic materials was also maintained. Dehydrogenase enzyme assay, enumeration of microbial population, and fractions of carbon were also undertaken at the end of incubation. Results of incubation experiment revealed that the amount of CO 2 –C mineralized during incubation increased with rise in temperature in all the treatments. The VRS treated soils registered higher mineralizable carbon at 15, 25, 35 and 45 oC. The rate of decomposition reaction was highest in soils that are treated with VRS and FYM. The highest activation energy was found in RHB amended soil (12.79 kJ mol -1 ) followed by RSB treated soil (12.71 kJ mol -1 ). Q 10 values represent the temperature dependency of the reaction. The results showed that all treatments had Q 10 values less than one. After incubation experiment, dehydrogenase activity as well as microbial population was found to decrease at 45 oC compared to the values at lower temperature. Comparatively, higher dehydrogenase activity and microbial population was registered in soils treated with VRS. The soils treated with VRS exhibited highest water soluble carbon (WSC), hot water extractable carbon (HWEC), microbial biomass carbon (MBC), and permanganate oxidizable carbon (POXC). However, biochar amended soils (RHB and RSB) registered higher value of total carbon. A field experiment was carried out to evaluate the efficacy of rice residues and their products in lowland with rice variety Uma as the test crop. The experiment consisted of ninetreatments with three replications viz., absolute control (T 1 ), Adhoc KAU organic POP (T 2 ), and treatments T 3 to T 9 comprised of soil test based nutrient recommendation along with FYM (T 3 ), VRH (T 4 ), VRS (T 5 ), RHB (T 6 ), RSB (T 7 ), RH (T 8 ), and RS (T 9 ) at 5t ha -1 . At weekly intervals Eh and pH were monitored. The soil and plant samples were collected at different stages of rice to analyse the effect of treatments on soil physical and chemical properties, fractions of nutrients in soil, nutrient content in plant, soil enzyme activity, and growth, yield and yield attributes of rice. Results of field experiment revealed that the application of residues and its products had a profound influence in lowering redox potential. The alkaline nature of rice residues and their products resulted in higher pH of experimental soil. Physical properties of post-harvest soil was improved by the application of T 6 and T 7 (soil test based nutrient recommendation + RHB and RSB). The application of T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ) was superior in increasing the nutrient status of post-harvest soil viz., C, N, P, Ca, Mg, S, Fe, Mn, Zn, and Si. While, K content was superior in T 7 (soil test based nutrient recommendation + RSB at 5 t ha -1 ). Soils receiving combined application of soil test based nutrient recommendation and VRS at 5 t ha -1 (T 5 ) recorded the highest WSC, HWEC, MBC, POXC, inorganic-N and P fractions, fractions of Ca and Mg at all the stages of crop. However, total- C, total hydrolysable-N, organic-P, and Si fractions were higher in biochar amended plots. Soil receiving joint application of soil test based nutrient recommendation +RSB at 5 t ha -1 (T 7 ) was statistically superior in fractions of K at all stages. Enzyme activity (dehydrogenase, urease, and acid phosphatase) was found to be highest in T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ), and it followed an increasing trend upto panicle initiation and thereafter it decreased in all treatments. The uptake of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B and Si were also highest in T 5 . With respect to the growth, yield and yield attributes of rice, application of soil test based nutrient recommendation + VRS at 5 t ha -1 (T 5 ) had superior effect. To conclude, the study has brought out the tremendous potential of rice straw and husk based biochar in improving soil physical properties and in elevating the total carbon content. However, the integration of soil test based nutrient recommendation with vermicompostedrice straw at 5t ha -1 (T 5 ) proved outstanding in augmenting soil fertility and crop productivity in the highly weathered, nutrient poor acidic lateritic soils.
Recycling of cashew (Anacardium occidentale L.) leaf litter and cashew apple through vermitechnology
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2016) Indu, V K; Jayasree Sankar, S
Rhizoctonia leaf blight of colocasia
(Kerala Agricultural University, 1995) Estclitta, S; Vilasini, T N; Jayasree Sankar, S
Silicon availability of tropical soils with respect to rice nutrition
(Department of Soil Science and Agricultrural Chemistry, College of Horticulture,Vellanikkara, 2016) Arya Lekshmi, V; Jayasree Sankar, S
Silicon (Si) is the second most abundant element in soil. The amount of silicon in soil depends on parent material, soil type, pedogenic process and landscape. In soil solution, Si is present as monosilicic acid which is the only form that the plant can absorb from soil. The productivity of rice is comparatively low in soils of Kerala. As a ̳Si – accumulator‘, rice can benefit from Si nutrition. The application of Si can enhance growth and yield of rice. With this background, studies were conducted to categorize major rice growing soils of Kerala according to plant available silicon and to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. The release of silicon from different soils added with various silicon sources under different water regimes was also monitored. Soil samples were collected from five different locations representing major rice growing regions of Kerala viz., Kuttanad, Kole land, Pokkali, sandy and lateritic to categorize them according to plant available silicon. The available Si ranged from 7.70 mg kg -1 (sandy soil) to 34.91 mg kg -1 (Kole land soil) in the order Kole land > Pokkali > lateritic > Kuttanad > sandy soil. All the soils under study were categorized as low in available Si. The available Si had positive correlation with organic carbon, available N, Ca, Mg, Fe, Mn, Zn, exchangeable K, Ca, Mg and CEC and negative correlation with available boron, AEC and silica-sesquioxide ratio. These soils were subjected to fractionation of silicon. The major fractions of Si were mobile, adsorbed, organic, occluded, amorphous and residual Si. The percentage distribution of fractions of Si in these soils were in the order; residual Si > amorphous Si > occluded Si > organic Si > mobile Si > adsorbed Si. Quantity – intensity relationship of five major rice growing soils at two temperatures viz. 25 0 C and 40 0 C were studied. The highest buffer power was indicated by Kuttanad soil followed by Pokkali and sandy soils at 25 0 C. It clearly indicated that these soils have a higher power to retain Si on solid phase and replenish its concentration in soil solution as and when it is depleted through plant uptake or leaching. The equilibrium Si concentration and the amount of Si adsorbed by each soil were used to test the fitness of data to the adsorption isotherms viz., Langmuir, Freundlich and Temkin. The data obtained from the adsorption experiments fitted into Freundlich and Temkin equations, but not to Langmuir equation at 25 0 C. At 40 0 C no adsorption equations were obtained for any soil.An incubation study was conducted to know the extent of release of Si on addition of different sources of silicon such as rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate in five rice growing soils under submerged water regime (SWR) and field capacity water regime (FCWR). Addition of Si significantly increased the release of available Si in all soils except Kole land soil after a month. Kole land soil showed higher release of available Si after two months. The highest release of available Si was at SWR in case of Kole land and Kuttanad soil, where as Pokkali, sandy and lateritic soils showed more release of available Si at FCWR. Irrespective of soils, treatment with sodium silicate showed higher release of available Si. Total Si showed a decreasing trend over the period of incubation for three months in all the soils. A field experiment was conducted at Agronomic Research Station, Chalakudy to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. Rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate were used as source of Si along with fertilizers as per package of practice recommendation (NPK alone). The maximum number of panicles per hill, number of spikelets per panicle, thousand grain weights and minimum number of unfilled grains per panicle were recorded in treatment with calcium silicate application. The maximum grain yield of 6.90 t ha -1 was recorded in treatment T 5 (T 2 + Calcium silicate) and significantly superior (fig.54) over all other treatments. This increase in yield may be due to the effect of application of Si on soil fertility, nutrient uptake, and plant growth. The direct effect of Si fertilization on increased number panicle per hill, number of spikelets per panicle, and thousand grain weight and decreased number of unfilled grains per panicle might be the reason for increased grain and straw yield in treatment with calcium silicate. The treatment with POP + sodium silicate showed the highest uptake of Si by grain and straw of rice. The sources of Si had no residual effect on grain and straw yield of succeeding rice crop. In general, sandy soil low in available Si had a high response to applied Si in achieving higher grain yield.
Silicon availability of tropical soils with respect to rice nutrition
(Department of Soil Science and Agricultrural Chemistry, College of Horticulture,Vellanikkara, 2016-03-28) Arya Lekshmi V; Jayasree Sankar, S
Silicon (Si) is the second most abundant element in soil. The amount of silicon in soil depends on parent material, soil type, pedogenic process and landscape. In soil solution, Si is present as monosilicic acid which is the only form that the plant can absorb from soil. The productivity of rice is comparatively low in soils of Kerala. As a ̳Si – accumulator‘, rice can benefit from Si nutrition. The application of Si can enhance growth and yield of rice. With this background, studies were conducted to categorize major rice growing soils of Kerala according to plant available silicon and to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. The release of silicon from different soils added with various silicon sources under different water regimes was also monitored. Soil samples were collected from five different locations representing major rice growing regions of Kerala viz., Kuttanad, Kole land, Pokkali, sandy and lateritic to categorize them according to plant available silicon. The available Si ranged from 7.70 mg kg -1 (sandy soil) to 34.91 mg kg -1 (Kole land soil) in the order Kole land > Pokkali > lateritic > Kuttanad > sandy soil. All the soils under study were categorized as low in available Si. The available Si had positive correlation with organic carbon, available N, Ca, Mg, Fe, Mn, Zn, exchangeable K, Ca, Mg and CEC and negative correlation with available boron, AEC and silica-sesquioxide ratio. These soils were subjected to fractionation of silicon. The major fractions of Si were mobile, adsorbed, organic, occluded, amorphous and residual Si. The percentage distribution of fractions of Si in these soils were in the order; residual Si > amorphous Si > occluded Si > organic Si > mobile Si > adsorbed Si. Quantity – intensity relationship of five major rice growing soils at two temperatures viz. 25 0 C and 40 0 C were studied. The highest buffer power was indicated by Kuttanad soil followed by Pokkali and sandy soils at 25 0 C. It clearly indicated that these soils have a higher power to retain Si on solid phase and replenish its concentration in soil solution as and when it is depleted through plant uptake or leaching. The equilibrium Si concentration and the amount of Si adsorbed by each soil were used to test the fitness of data to the adsorption isotherms viz., Langmuir, Freundlich and Temkin. The data obtained from the adsorption experiments fitted into Freundlich and Temkin equations, but not to Langmuir equation at 25 0 C. At 40 0 C no adsorption equations were obtained for any soil.An incubation study was conducted to know the extent of release of Si on addition of different sources of silicon such as rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate in five rice growing soils under submerged water regime (SWR) and field capacity water regime (FCWR). Addition of Si significantly increased the release of available Si in all soils except Kole land soil after a month. Kole land soil showed higher release of available Si after two months. The highest release of available Si was at SWR in case of Kole land and Kuttanad soil, where as Pokkali, sandy and lateritic soils showed more release of available Si at FCWR. Irrespective of soils, treatment with sodium silicate showed higher release of available Si. Total Si showed a decreasing trend over the period of incubation for three months in all the soils. A field experiment was conducted at Agronomic Research Station, Chalakudy to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. Rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate were used as source of Si along with fertilizers as per package of practice recommendation (NPK alone). The maximum number of panicles per hill, number of spikelets per panicle, thousand grain weights and minimum number of unfilled grains per panicle were recorded in treatment with calcium silicate application. The maximum grain yield of 6.90 t ha -1 was recorded in treatment T 5 (T 2 + Calcium silicate) and significantly superior (fig.54) over all other treatments. This increase in yield may be due to the effect of application of Si on soil fertility, nutrient uptake, and plant growth. The direct effect of Si fertilization on increased number panicle per hill, number of spikelets per panicle, and thousand grain weight and decreased number of unfilled grains per panicle might be the reason for increased grain and straw yield in treatment with calcium silicate. The treatment with POP + sodium silicate showed the highest uptake of Si by grain and straw of rice. The sources of Si had no residual effect on grain and straw yield of succeeding rice crop. In general, sandy soil low in available Si had a high response to applied Si in achieving higher grain yield.
Spatial and temporal variations in nutrient dynamics in Pokkali soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2022) Silpa, P; Jayasree Sankar, S
The Pokkali soils (Typic Sulfaquents) are low land soils situated below the mean sea level, located along the coastal tracts of Alappuzha, Ernamkulam and Thrissur districts. These soils are acid saline in nature where shrimp/prawn farming is practiced during high saline phase (December to April) coinciding with sea water entry followed by cultivating the salt tolerant Pokkali rice during low saline phase (June to October) when the dilution of salts occurs after South West monsoon. Only very few studies have been undertaken so far on nutrient status in Pokkali soils. Wide variations in nutrient content ranging from deficient to toxic level were reported in these studies. A comprehensive study is very much essential to unravel the seasonal and temporal variations of nutrient dynamics in Pokkali soils. The soil samples (lowland soils and neighbouring upland soils) from different land use systems and the water samples (both standing water and nearby brackish water inundating the Pokkali tract) were collected at bimonthly intervals starting from June 2017 to April 2018 to understand the nutrient dynamics in these soils with respect to spatial and temporal variation and to find out the influence of source water on them. Physico-chemical properties and biological properties of the collected soils were analysed. Salt water intrusion during high saline phase into Pokkali fields caused drastic increase in electrical conductivity, decrease in soil pH and associated changes in available plant nutrients. A gradual decrease in redox potential from June to October and increase from December to April were also observed as an influence of sea water intrusion. The south west monsoon received during the low saline phase played a significant role in diluting soil salinity and loss of H + ions from top soil, thus affecting the soil nutrient dynamics in total. High content of available plant nutrients and the change in nutrient content with respect to spatial and temporal variations were observed in low land soils compared to the nearby upland soils. Spatial variation of all available nutrients except phosphorus was highly influenced by the nearness of brackish water rather than the type of land use system. Highest available phosphorus recorded in paddy alone land use might be due to the phosphorus mineralisation from left out crop stubbles in paddy field. Some land uses in uplands showed deficiency of available Ca, Mg and B also. In terms of temporal variation, all nutrients except available phosphorus remained very high during high saline phase as influenced by marine water whereas availability of phosphorus was highly influenced by soil pH. High acidity and salinity during high saline phase adversely affected the soil biological properties. Fractionation of phosphorus and copper was carried out to study their major fractions and to ascertain their contribution to the available pool. All the P fractions were high in Pokkali soil. Temporal variation of all the P fractions was also prominent in Pokkali soil. Ws-P, Ca-P and residual-P were very high in October (low saline phase) whereas other fractions were high in April (high saline phase). Effect of land uses on P fractions was absent except for Org-P and Ca-P. Temporal variation of all the Cu fractions was clearly evident in Pokkali soil. Ws-Cu, Ex-Cu and residual Cu were high in April (high saline phase). All other fractions were high in October (low saline phase). Land uses did not show any direct effect on distribution of copper fractions. All the land uses showed same trend in copper fractions across the seasons. Phosphorus adsorption was high in April (high saline phase) whereas Cu adsorption was high in October (low saline phase). L and S-shaped curves were obtained for P and Cu adsorption respectively. Adsorption of P and Cu increased with increase in soil temperature. Adsorption of P and Cu among various soil textural classes followed the order clay>clay loam>sandy clay loam>loam>silt loam. Adsorption of P was mainly in inorganic forms ie. oxide and oxy hydroxides of Fe and Al surface whereas that of Cu was mainly in organic form. Freundlich adsorption isotherm was found as the best to explain the adsorption of P and Cu in Pokkali soils. Adsorption of both P and Cu was spontaneous and endothermic in nature. Low and high saline phases attributed to variations in physico-chemical and biological properties of Pokkali soils. South West monsoon caused leaching losses of nutrients particularly potassium, sulphur, magnesium and boron during low saline phase. The presence of brackish water source nearer to field had more effect on nutrient dynamics in Pokkali soils, rather the type of land use system. The influence of temperature on nutrient was visible in the quantity –intensity relations of P and Cu. The present study has clearly shown that the nutrient dynamics in Pokkali soils is influenced more by temporal variations than the spatial variations.
Studies on the root activity pattern of black pepper employing radiotracer technique
(Department of soil science and agricultural chemistry, College of Horticulture, Vellanikkara, 1985) Jayasree Sankar, S; Wahid, P A
An investigation on the root activity pattern of black pepper vine and allied aspects was conducted employing phosphorus-32. The results indicated that the active root zone of black pepper vine trailed either on erythrina or on teak pole is in a soil column of 30 cm radius around the vine. It is suggested that fertilizer application to pepper vines may be done in a semicircle of 30 cm radius facing the vine for the most effective utilization of the added nutrients. Growing the vine in association with erythrina as support was found to reduce the uptake of 32p by at least 20 per cent as compared to that grown on teak pole. The active root system of erythrina was found to be more extensive than the vine reaching upto 60 cm from the pepper plant. The absorption of 32p by the climbing roots of the vine was found to be insignificant. A method of leaf sampling for 32p assay in black pepper vine as well as a method of soil injection of 32p solution into root zone of crop plants was developed. Annual exhaust of nutrients by way of harvest of 1.284 kg dry pepper was found to be 38.5g N, 36.7 g K, 14.9 g Ca, 13.7 g Mg, 2.2 g P, 1.37 g S, 218 mg Fe, 155 mg Mn, 28 mg Zn and 47 mg of Cu. From the defoliation of erythrina, an annual recycling of 0.7 kg dry matter containing 25.7 g N, 0.94 g P, 6.5 g K, 20 g each of Ca and Mg, 0.8 g S, 131.4 mg Fe, 1008 mg Mn, 13 mg Zn and 14.2 mg Cu may be expected.
Suitability of azolla(azolla pinnata) for biogas slurry enrichment
(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellakikkara, 2012) Bishnu Prasad Paudel; Jayasree Sankar, S
A study on “Suitability of azolla (Azolla pinnata) for biogas slurry enrichment” was conducted during 2010-11 at College of Horticulture, Vellanikkara to evaluate the optimum ratio of cow dung and azolla for biogas slurry enrichment, to identify the best material to prepare quality organic manure from the enriched slurry and also to adjudge the crop response to enriched organic manure. To attain the objectives, three separate experiments were conducted in a phased manner. In order to determine the optimum ratio of cow dung and azolla for biogas slurry enrichment, the floating drum biogas digesters of 0.5 m3 capacity were used. The different proportion of the substrates tried were cow dung alone and cow dung and azolla in 1: 0.25, 1: 0.5, 1: 0.75 and 1: 1 ratio. The results indicated that mixing of cow dung and azolla in a proportion of 1: 0.5 produced the highest volume of gas (0.29 m3 kg-1 TS) in 20 days of Hydraulic Retention Time (HRT). But the proportion of 1: 1 favored in terms of N (3.44 per cent) content in slurry followed by 3.23 per cent in 1: 0.75 ratio. These treatments were designated as enriched slurry I (3.44 per cent N, 0.74 per cent P and 2.93 per cent K) and enriched slurry II (3.23 per cent N, 0.77 per cent P and 2.91 per cent K). Addition of azolla increased pH from 7.1 to 7.8 but decreased the total solids of slurry from 5.40 per cent in cow dung alone to 2.68 per cent in the ratio of 1: 1. For identifying the best material for preparing quality manure from the enriched slurry, it was mixed with saw dust, coir dust and powdered coconut leaves which varied in the nutrient content and C/N ratio. Based on the nutrient content, powdered coconut leaves were identified as the best material and the requirement was 612 g per litre in enriched slurry I and 607 g per litre for enriched slurry II. Crop response to the enriched manure I and II was assessed in pot culture with rice (variety- Jyothy) as the test crop. The treatments were control (T1), NPK+FYM (T2), FYM alone (T3), enriched manure I (T4), enriched manure II (T5), enriched manure I+NPK (T6) and enriched manure II+ NPK (T7). The grain (44.97 g pot-1) and straw (72.73 g pot-1) yield was maximum when the crop was nourished with enriched manure II in association with the recommended dose of chemical fertilizers. Crop uptake of N (4260 mg pot-1) and K (4263 mg pot-1) was also the highest in this treatment. Soil physico-chemical properties were also favorably influenced by the manure application. A shift in pH from 4.7 to 5.4 was obtained consequent to applying enriched manure I. Soil status of available N (1536 mg kg-1) and available K2O (471 mg kg-1) was the highest when enriched manure II was applied along with the recommended dose of chemical fertilizers. The content of available P2O5 in soil was the maximum (52.7 mg kg-1) when chemical fertilizers were excluded from this treatment.
Sulphur dynamics in major rice-growing soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2022) Unnikrishnan, R; Jayasree Sankar, S
Sulphur has been recognized as an essential nutrient to plants and it is ranked as fourth among major plant nutrients after nitrogen, phosphorus, and potassium. Most of the soils in Kerala are rich in total S and the maximum amount of sulphates has been reported in Kari and Pokkali soils. Representative soil samples were collected from seven different rice growing tracts falling under different agro-ecological units (AEU) of Kerala for the study entitled Sulphur dynamics in major rice-growing soils of Kerala. Five samples each were collected from various locations pertaining to a particular soil type for initial characterisation. In addition three soil and plant samples were also collected from each soil type at active tillering and harvest stage of rice crop. The study aims at understanding sulphur dynamics in major rice soils of Kerala and its relationship with that of carbon, nitrogen and phosphorus. It also envisages at unfolding the antagonism/ synergism between sulphur and other nutrients, if any. Sixteen out of 35 samples belonged to the category of strongly acidic to moderately acidic. It can be concluded from characterisation study that the sandy soils of Onattukara was low in terms of fertility wherein Pokkali soils, Kole land and Kari soils of Kuttanad were high with respect to soil fertility. None of the soils were found deficient in available sulphur with Pokkali soils being the remarkably highest. The low land brown hydromorphic laterite and Onattukara sandy soils had relatively lower sulphur content. The Kari soils accounted for highest microbial biomass carbon and aryl sulphatase activity. The estimated soil pH was slightly elevated at active tillering and harvest stage. The sulphur exhibited an antagonistic relationship with phosphorous, potassium as well as manganese Fractionation of S was conducted at three stages to find out the dominant different forms of sulphur. The Pokkali soils and Onattukara sandy soils had the highest as well as lowest value for all the sulphur fractions before cropping. The Kari soil concluded the highest total organic sulphur at active tillering and harvest stage. All the sulphur fractions were positively influenced by microbial biomass carbon and aryl sulphatase activity. An identifiable positive relation existed between available nitrogen and total organic sulphur as well. The C:S ratio was high in Laterite soil and lowest in Pokkali soil at all the three stages. The Onattukara sandy soil and Laterite soil accounted for the highest N:S ratio wherein Kari soil and Pokkali soil had the lowest ratio. The decreased C:S and N:S ratio contributed to the raised plant available sulphur in soil. Sulphur adsorption experiment was conducted at 25 ℃ as well as 40℃ and quantity-intensity relations were carried out based on data. While The samples from Pokkali and Kari soil exhibited desorption of sulphur at both the temperatures (25 ℃ and 40 ℃) studied, it was found to get adsorbed in the case of Laterite soil and Onattukara sandy soils at both 25 ℃ and 40 ℃.